This invention relates to the field of boxes for electrical wiring devices and snap-in locking devices which enable mounting such boxes in a wall by inserting through a hole provided for such purposes whereupon the locking device snaps back to hold the box in place.
Many of the previous devices of this type have been formed integrally as part of the side walls or top and bottom walls of the box, particularly in the case of plastic or non-metallic wiring device boxes. Such integrally formed snap-in devices have proven to be unsatisfactory in practice because they depend on the resilience of the side walls or top and bottom walls of the plastic boxes to provide the flexing and rebound, or the snap-back characteristic. Such boxes with integrally formed snap-in type locking devices are usually made of thermoplastic materials which do not always return to the original position after being flexed. The side walls, for example, of thermoplastic electrical boxes tend to bow inwardly and to become softened when temperatures rise. When this happens the integrally formed locking members are also drawn inwardly and become softened whereby the boxes become loose and may even be unintentionally withdrawn from their wall mountings. There is also a limited and undesirable amount of movement between the flexed and unflexed position of the locking members which are integrally formed on the wall of a wiring device box. A separate detachable snap-in locking device can easily overcome this problem because it can be made of other materials such as metals which have excellent rebound characteristics, as well as good temperature characteristics.
Some of the known prior art locking devices of the snap-in type for electrical wiring device boxes can be removed from the box by cutting the rivets with which they are attached or by removing the screws which secure the devices to the box. However, such devices are made for particular types of wiring device boxes and are not for universal use with wiring device boxes of all types, including those which do not incorporate the special features needed for the prior art devices to function.
Another problem with prior art locking devices of the snap-in type is spacing of the snap-in members or fingers from the front open wall of the box a proper distance to enable the forward edges of the snap-in member to bear tightly against the inner surface of the mounting wall when the box has been finally secured in its proper position, which usually requires that the open front wall of the box is either flush with the other surface of the mounting wall or set inwardly therefrom a distance so the box in any event does not project outwardly from the outer surface of the wall on which it is mounted. When this is done with boxes having known prior art locking devices of the snap-in type, the forward edges of the snap-in members are often set back from and spaced apart from the inner surface of the mounting wall, and the box is therefore not mounted tightly and securely in place.
The detachable locking device of the snap-in type in accordance with the present invention overcomes the foregoing problems and difficulties.